2011 Annual Report
1a.Objectives (from AD-416)
1. Use data from genome-wide systematic analysis to determine the molecular and biological changes that occur in A. flavus upon infection of corn and other crops.
2. Identify mechanistic and molecular requirements for transcriptional regulation of aflatoxin biosynthesis and fungal survival to develop targets for intervention.
3. Establish effects of abiotic (environmental, nutritional) factors on fungal development and toxin production by aflatoxin-producing fungi.
1b.Approach (from AD-416)
Aflatoxins (AFs) are polyketide-derived, toxic, and carcinogenic secondary metabolites produced by Aspergillus flavus on corn, peanuts, cottonseed, and tree nuts. While biosynthesis of these toxins has been extensively studied, much less is known about what causes the fungi to produce AFs under certain environmental conditions and only on certain plants. Our goal is to determine the dynamics of interaction among the key nutritionally and environmentally induced transcription factors necessary for production of AF in order to develop novel inhibitors to one or more of these factors to prevent AF formation in crops. We will use gene microarray, yeast two-hybrid, and chromatin immunoprecipitation assays to determine which critical AF transcription-associated proteins are affected by physiological stress, environmental and soil conditions, and interactions of the fungus with plants. Interactions among key known or to be discovered AF biosynthesis regulatory factors, such as LaeA, VeA, AflJ, and AflR, will be examined by these methods. We will examine the effects of known natural (plant-derived, such as volatile aldehydes) inhibitors of AF production on key components of the AF transcription machinery to ultimately design safe, inexpensive chemicals that inhibit proteins unique to fungal secondary metabolite biosynthesis. We expect to identify safe and effective inhibitors for applications on crops intended for consumption by humans or animals.
This report documents progress for the parent Project 6435-41420-006-00D "Control of Aflatoxin Production by Targeting Aflatoxin Biosynthesis" which started January 2011 and continues research from Project 6435-41420-005-00D "Aflatoxin Control through Targeting Mechanisms Governing Aflatoxin Biosynthesis in Corn and Cottonseed." We are continuing to prepare ribonucleic acid (gene products), RNAs, from the fungus Aspergillus (A.) flavus grown on corn for microarray studies (i.e. looking at which genes in the fungus are activated when the fungus comes in contact with the crop). We are also comparing genomes (all of the genes of this type of fungus) present in the field with a view to determine the molecular and biological changes that occur in A. flavus upon infection of corn and other crops. We are using a two-hybrid system (a technique that measures interactions amongst proteins) to assess which proteins may be essential within the fungus that are responsible for regulating the expression of specific genes that are responsible for the production of aflatoxins. The aim is to find requirements for fungal survival to develop targets for intervention. We are in the process of identifying targets involved in aflatoxin biosynthesis inhibition by volatile compounds produced by plants. Ultimately we will establish the effects of environmental and nutritional factors required for fungal development and toxin production by these harmful fungi (toxin producers) so that we can develop strategies for their control.
Rosas-Taraco, A., Sanchez, E., Garcia, S., Heredia, N., Bhatnagar, D. 2011. Extracts of Agave americana inhibit aflatoxin production in Aspergillus parasiticus. World Mycotoxin Journal. 4(1):37-42.